Ozone has highly oxidising properties and is used, preferably in diluted form, for sterilisation of water. For example, sewage water can be treated with the aim of decomposing or eliminating environmentally or health hazardous substances therefrom, as well as removing unpleasant odours from the water, and drinking water can be pre-treated with the intention of improving the quality of the water. Other areas of use are e.g. as a bleaching agent in the paper industry, for air cleaning and for performing certain oxidation reactions within organic chemistry.
Ozone is produced by letting oxygen, or a gas rich in oxygen, pass through an electrical discharge. Oxygen or an oxygen-rich gas is thereby allowed to flow through a chamber in an ozone generator, said chamber being defined either by two co-axial tubes, or a series of plates, between which tubes or plates an electrical discharge is taking place. In this description, the terms space and chamber are used as denomination for the same thing, i.e. the location inside the ozone generator where existing oxygen or oxygen-rich gas is converted into ozone. The first mentioned type of ozone generator is, for industrial purposes, very large and bulky, and difficult and costly to manufacture and maintain. The second type of ozone generator, here called the plate type, is less demanding in terms of economy and space. As the demand for reliable, large capacity ozone generators tends to increase, plate type ozone generators are often arranged on top of each other in blocks, whereby larger ozone generator systems can be obtained. Some examples of such ozone generator systems are disclosed in WO 97/01507 by Arlemark, and in U.S. Pat. No. 5,435,978 by Yokomi.
One problem associated with ozone generators is connected with the chamber, in which oxygen in the form of oxygen gas or a gas rich in oxygen is converted into ozone, having at least one delimiting surface made of a dielectric material, a so-called dielectric. This dielectric is used for the purpose of generating a corona during the discharge between a high-voltage electrode and ground, and normally consists of a ceramic or glass material. Pressure variations in the gas fed into the chamber, for example caused by pressure chocks in the system when the gas supply is switched on or off, will generate high strains in the ceramic material, entailing a risk of cracking it. This problem naturally also tends to increase if, with the aim of increasing the capacity, an increased pressure of the introduced oxygen gas is used. If, furthermore, there is an imbalance in pressure and/or flow between different generators, and between the inlet and outlet ports of the individual generators, the stress upon the total system will be even higher. In ozone generator systems arranged in blocks, it is a further problem if the entire system has to be closed down if one generator breaks down.
Another problem is associated with the very reactive properties of the ozone, entailing a tendency for hoses and rubber seals to deteriorate and cause leakage. This applies for example to the seals and gas lines required in connection with the oxygen inlets and the ozone outlets. In ozone generator systems having several generators in a block, this problem will become especially obvious, as at least one inlet and one outlet is required for each generator.
Another problem connected to large ozone generator systems is that they have to be arranged at the location where the ozone is to be used, due to the short life span of the ozone before it disintegrates. As a consequence of the ancillary equipment, such as the connections required for oxygen, ozone and cooling water, having to be constructed on site, the cost of installation tends to become very high.